Method for producing metallic filaments

ABSTRACT

A process for producing long continuous lengths of metallic filaments is disclosed which process comprises securing four flat plates of a first metal to each of the elongated sides of a billet of a second metal and having a cross section in shape of a rectangle, by edge welding each of the plates. The resulting assembly is essentially void free. The rectangular cross section of the billet is reduced while being elongated by hot rolling. The resulting elongated rectangular structure, having a core of the second metal and a cladding of the first metal over the elongated sides, is divided into a plurality of elements of the same lengths. The elements are inserted into a hollow metal tube open at both ends having a rectangular cross section in a manner to essentially eliminate the voids and with their longitudinal axes and the longitudinal axis of the tube essentially parallel. Ends of the tube are sealed and the sealed unit is reduced in cross section and elongated by hot rolling. The other materials are removed from the resulting filaments of the first metal yielding materials suitable for weaving into metal cloth.

[ 1 Oct. 2, 1973 METHOD FOR PRODUCING METALLIC FILAMENTS [75] Inventors:Arnold J. Gottlieb, Colonia; George A. Majesko, Glen Ridge, both of NJ.

[73] Assignee: Wilbur B. Driver Company, Newark,

[22] Filed: July 15, 1971 [21] Appl. No.: 162,989

Related US. Application Data [63] Continuation-impart of Ser. No.820,556, April 30,

1969, abandoned.

2,077,682 4/1937 Everett 29/423 UX 2,711,966 6/1955 Watson et al.29/470.9 UX 3,277,564 10/1966 Webber et al. 29/419 3,394,2l3 7/1968Roberts et al. 29/419 X FOREIGN PATENTS OR APPLICATIONS 631,584 11/1949Great Britain 29/l87.5

Primary Examiner-Charles W. Lanham Assistant Examiner-D. C. Reiley, lllAttorney-Norman J. OMalley et al.

[57] ABSTRACT A process for producing long continuous lengths ofmetallic filaments is disclosed which process comprises securing fourflat plates of a first metal to each of the elongated sides of a billetof a second metal and having a cross section in shape of a rectangle, byedge welding each of the plates. The resulting assembly is essentiallyvoid free. The rectangular cross section of the billet is reduced whilebeing elongated by hot rolling. The resulting elongated rectangularstructure, having a core of the second metal and a cladding of the firstmetal over the elongated sides, is divided into a plurality of elementsof the same lengths. The elements are inserted into a hollow metal tubeopen at both ends having a rectangular cross section in a manner toessentially eliminate the voids and with their longitudinal axes and thelongitudinal axis of the tube essentially parallel. Ends of the tube aresealed and the sealed unit is reduced in cross section and elongated byhot rolling. The other materials are removed from the resultingfilaments of the first metal yielding materials suitable for weavinginto metal cloth.

3 Claims, 6 Drawing Figures 51 [3000 [J @1300 [3 DQEJ C] [HOOD p OBOE]Pmmmnmms 3,762,025

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INVENTORS. ARNOLD J. GOTTLIEB & GEORGE A. MAJESKO M cow ATTORNEY METHODFOR PRODUCING METALLIC FILAMENTS CROSS REFERENCE TO RELATED APPLICATIONThis application is a continuation-in-part of Ser. No. 820,556, filedApr. 30, 1969, now abandoned and assigned to the assignee of the presentinvention.

BACKGROUND OF THE INVENTION This invention relates to a multi-stepprocess for producing metal filaments. More particularly it relates to aprocess utilizing hot rolling, in both steps.

Several processes are known for the production of metal fibers orfilaments. For example, in US. Pat. No. 3,277,564 a process is disclosedwherein filaments are formed by forming a bundle of wires inside asheath of a dissimilar metal, then drawing the bundle through a seriesof successive dies. Since round cross sectional shapes of the sheath arerequired in order to draw the bundle, any bundle has a relatively largeportion thereof as voids. To obtain a reduction in the wire size, thetotal reduction in the cross-section of the bundle is relatively high.

U.S. Pat. No. 3,394,213 also discloses a process by which metalfilaments are formed by construction of bundled wires or tubularelements by forming the bundled wires or elements into a billet andsubjecting the billet successively to a hot forming constriction andsubsequently drawing constriction. When the voids between the wires arenot filled with a suitable particulate powder the billet is firstcompacted by axial shortening the billet, thus radially compacting thebillet to reduce voids. Thereafter the billet is subject to hotextrusion.

It can be seen that the prior art methods each start with initialmaterials having a relatively large percentage of voids. Although thedifficulties with voids are recognized, the solutions thereto eitherinvolve filling the voids with a filler material which inherently lowersthe efiiciency of the process or compacting the initial billet which isan additional step and adds an inherent inefficiency.

Additionally, when core materials of a first metal having a circularcross-sectional area are sheathed with a second metal and are placed incontact with each other to form a billet inside a casing, the mutualcontact of the sheathed material is along a line. When the billet issubjected to compaction or constriction pressures, there is a tendencyfor the sheath and the casing to flow into any voids thus reducing itsthickness nonuniformly and can lead to sheath rupture. If the sheaththickness is insufficient to fill the voids the cores come into contactwith each other and can weld to each other. These problems areintensified with hot rolling thus hot rolling is not practical if thereis substantial voids in the billets.

It is believed, therefore, that a process using void free rectangularcross section metal fibers via hot rolling without compaction or use offiller materials is an advancement in the art.

SUMMARY OF THE INVENTION In our invention, the peripheral side surfacesof an elongated billet of uniform rectangular cross section of a secondmetal, for example, a billet, are each clad with a flat plate of a firstmetal. These plates are edge welded together to the member whereby anessentially void free assembly is formed.

The assembly is then hot rolled whereby it is reduced in cross sectionand is correspondingly elongated. The elongated member which has arectangular cross section is cut into a plurality of like elements ofthe same length. Each element has a core of the second metal clad withthe first metal.

A hollow tube of rectangular cross section with opposite open ends isformed of a metallic component which is dissimilar to the second metaland which can, but need not, be dissimilar to the first metal. This tubeis filled with a plurality of said elements which have theirlongitudinal axes parallel with each other and with the longitudinalaxis of the tube whereby the elements form an essentially void freebundle. The tube is then sealed and hot rolled. The individual elementsare reduced in cross section and are elongated to form filaments of verysmall cross section imbedded in a metallic matrix.

Thereafter, the composite (which if necessary can be further reduced bycold drawing and annealing) can be immersed in acid media which will notattack the second metal but which will etch away all material other thanthe first metal, leaving only the filaments. These filaments formmetallic yarn which can be used in weaving or the like.

Alternatively, the composite need not be etched but can be used withoutfurther processing as a fiber reinforced structure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the initial step incladding the first component;

FIG. 2 is an end view of the billet showing location of longitudinalwelds;

FIG. 3 is a perspective view of the billet showing location of the endwelds;

FIG. 4 shows in cross section the shape of the clad billet after hotrolling;

FIG. 5 is a cross sectional view of the geometry employed in furtherstep of our process; and

FIG. 6 illustrates the member obtained after still a further step in ourprocess.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For a betterunderstanding of the present invention, together with other and furtherobjects, advantages, and capabilities thereof, reference is made to thefollowing disclosure and appended claims in connection with theabove-described drawings.

Referring now to FIGS. l7, there is shown a first component 10 of 304stainless steel with a cross section in the form of a square two and onehalf inches on a side. Flat steel side plates 12 are secured to theflat, cleaned and ground sides of the billet 13 by longitudinal comerwelds l4 and end welds 16.

The steel plate covered billet was then processed in the followingmanner. It was first hot rolled at a temperature of 2,000 F through asuccession of diamond and oval passes to reduce the cross section of theplate covered billet, for example, to a square 0.25 inch on a side asshown at 20.

A succession of segments of like length were cut from the above. Afterdescaling, these lengths were then packed in a hollow steel tube 24 of 3X 3 inch cross section having a one-fourth inch thick wall. The voidspace is essentially eliminated when segments of square cross sectionare used.

This tube was then sealed and again hot rolled as before whereby theindividual cores of element 20 form elongated filaments 26 of smallcross section, imbedded in a metallic matrix 28. Illustratively, thecomposite can have a diameter of 0.25 inch at this stage.

Thereafter the composite was cold drawn and annealed to reduce thediameter of the individual filaments to a desired value as for example0.0005 inch. The drawn composite can then be treated as for example bydipping into a dilute nitric acid bath until the steel is etched awayleaving only the fine filaments of stainless steel which can be used inweaving, knitting or the like.

Alternatively, this last step can be omitted whereby the composite canbe used in applications where reinforced structures are of interest.

The portions of our process relating to the steps associated with FIGS.4-7 can be repeated as often as necessary to increase the number offilaments.

We have found that by using rectangular shaped materials throughout, thedifficulties of the prior art are avoided.

As previously mentioned the prior art methods each start with initialmaterials having a relatively large percentage of voids. Although thedifi'lculties with voids are recognized, the solutions thereto eitherinvolve filling the voids with a filler material which inherently lowersthe efficiency of the process or compacting the initial billet which isan additional step and adds an inherent inefficiency.

Additionally, when core materials of a first metal having a circularcross-sectional area are sheathed with a second metal and are placed incontact with each other to form a billet inside a casing, the mutualcontact of the sheathed material is along a line. When the billet issubjected to compaction or constriction pressures, there is a tendencyfor the sheath and the casing to flow into any voids thus reducing itsthickness nonuniformly and can lead to sheath rupture. If the sheaththickness is insufficient to fill the voids, the core members come intocontact with each other and can weld to each other. These problems areintensified with hot rolling, thus hot rolling is not practical if thereis substantial voids in the billets.

By using the special geometric shapes as defined herein the foregoingproblems are overcome. For example, excessive spreading during hotrolling is eliminated, the sheathing is uniform, no voids are present,therefore, no sheath rupture or core welding occurs and hot rolling isused throughout to produce the fibers.

While we have described our invention with particular reference to thedrawings, our protection is to be limited only by the terms of theclaims which follow.

What is claimed is:

l. A method for producing long continuous lengths of metallic filamentscomprising the steps of:

securing four flat plates of a first metal to each of the elongated flatouter sides of a billet of a second metal and having a cross section inthe shape of a rectangle by edge welding, the resulting assembly beingessentially free of voids;

reducing said assembly in cross section while elongating same by hotrolling to an elongated structure having a rectangular cross section;

dividing said elongated structure into a plurality of elements of thesame length each having a longitudinal axis;

inserting said elements into a hollow tube open at both ends and havinga cross section in rectangular shape in a manner to essentiallyeliminate the voids and having the longitudinal axes of the elementmutually parallel and parallel with the longitudinal axis of said tube,said tube being composed of a metallic component which is dissimilar tothe second metal and can, but need not be dissimilar to the first metal;

sealing said element carrying tube at both ends; and

reducing said sealed tube in cross section while elongating same by hotrolling whereby filaments of small cross section composed of said secondmetal are imbedded in a metallic matrix.

2. A method as set forth in claim 1 further including the additionalstep of removing said matrix from said filaments whereby the filamentsare exposed.

3. A method as set forth in claim 1 wherein said rectangle is a square.

1. A method for producing long continuous lengths of metallic filamentscomprising the steps of: securing four flat plates of a first metal toeach of the elongated flat outer sides of a billet of a second metal andhaving a cross section in the shape of a rectangle by edge welding, theresulting assembly being essentially free of voids; reducing saidassembly in cross section while elongating same by hot rolling to anelongated structure having a rectangular cross section; dividing saidelongated structure into a plurality of elements of the same length eachhaving a longitudinal axis; inserting said elements into a hollow tubeopen at both ends and having a cross section in rectangular shape in amanner to essentially eliminate the voids and having the longitudinalaxes of the element mutually parallel and parallel with the longitudinalaxis of said tube, said tube being composed of a metallic componentwhich is Dissimilar to the second metal and can, but need not bedissimilar to the first metal; sealing said element carrying tube atboth ends; and reducing said sealed tube in cross section whileelongating same by hot rolling whereby filaments of small cross sectioncomposed of said second metal are imbedded in a metallic matrix.
 2. Amethod as set forth in claim 1 further including the additional step ofremoving said matrix from said filaments whereby the filaments areexposed.
 3. A method as set forth in claim 1 wherein said rectangle is asquare.